I used Ubuntu in 2004 right when I started college as a comp-sci student. It was the only distro that worked with my laptop with very minimal effort. I also love the package management (though Brew on OSX is a close second).

Point #2, negativity, is one of the more surprising things I've had to deal with. It leaks into your personal life, and nobody likes "that guy/girl" who is critical and pessimistic about every little thing.